Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
  • B60C1/0016—Compositions of the tread
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C11/00—Tyre tread bands; Tread patterns; Anti-skid inserts
  • B60C11/0008—Tyre tread bands; Tread patterns; Anti-skid inserts characterised by the tread rubber
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
  • C08K5/0016—Plasticisers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L47/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds; Compositions of derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
  • C08L9/06—Copolymers with styrene
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C11/00—Tyre tread bands; Tread patterns; Anti-skid inserts
  • B60C11/0008—Tyre tread bands; Tread patterns; Anti-skid inserts characterised by the tread rubber
  • B60C2011/0016—Physical properties or dimensions
  • B60C2011/0025—Modulus or tan delta

Definitions

• This invention relates generally to vehicle tires and more particularly, to tire treads and materials from which they are made.
• Particular embodiments of the present invention include treads and tires having such, treads that have improved characteristics breaking the compromise between wear and wet braking,
• Such embodiments include a tread for a tire comprising a rubbe composition based upon a cross-linkable, composition having greater than 90 phr of an elastomer component selected from st rene- butadiene, rubber (SBR), poiybutadiene rubber or combinations thereof having a glass transition temperature of between -.100 °C and Jess than -50° C and a plasticizing system.
• Embodiments include having a plasticizing system, comprising between 5 phr and 120 phr of a plasttcizmg resin haying a Tg of at least .
• a plasticizing oil 25° C and between 0 phr and ' 60 phr of a plasticizing oil.
• a plasticizing oil 25° C and between 0 phr and ' 60 phr of a plasticizing oil.
• Th cross-linkable rubber composition may further include a curing system.
• Particular embodiments may include the elastomer component having a Tg of between -90 °C and -60 °C and/or may further have the elastomer component included in. an amount of at least 95 phr.
• FIG. 1 is a graph that, compares the wet. braking and wear performance for tires having treads manufactured from different rubber compositions.
• Particular embodiments of the present invention include tires and treads for vehicles that surprisingly break a compromise faced by fire designers; i.e., an increase in the tread wear of a- tire often results in a decrease in the wet. braking performance of the tire.
• This compromise may be broken by forming unique tire treads from a. rubber composition that includes a rubber component having a low glass transition- temperature (Tg) of between -100 °C and less than.
• Tg glass transition- temperature
• -50 C and a p!asticizing system that may include both a high loading of a piastic-izing resin having a high Tg and a plasticiziug liquid,
• the tires and treads disclosed herein are formed of a rubber composition that includes a rubber component that is made up entirely or almost entirely of a rubber having a low glass transition temperature (Tg), i.e., between -100 a C and less than -50° C.
• Tg glass transition temperature
• Such useful rubber components may include, for example, SBR, poiybuiadtene or combinations thereof. While particular embodiments of the present invention may utilize only the low Tg rubber as the rubber component of a rubber composition, other embodiments may include u to 9 parts by weight per hundred parts of rubber (phr) of one or more other diene rubbers blended into the rubber composition,.
• phr is "parts per hundred parts of rubber by weight” and is a common measurement in the ait wherein components of a rubber composition are measured relative to the total, weight -of rubber in the composition, ie,, parts by weight of the component per 100 parts by weight of the total rubber(s) in the composition.
• based upon is a term recognizing that embodiments, of the present invention are made o -vulcanized or cured rubber compositions that were, at the time of their assembly, uncured..
• the cured rubber composition is therefore "based upon” the uncured rubber composition.
• the cross-linked rubber composition is based upon or • comprises the constituents of the cross-linkable rubber composition.
• a tire tread is the road-contacting portion of a -vehicle tire that extends circnmferentialiy about the tire. It is designed to provide the handling characteristics required by the vehicle; e.g., traction, dry braking, wet. braking, cornering and so forth - all being preferably provided with a minimum amount, of noise being generated and at a low rolling resistance.
• Treads of the type that are disclosed herein include tread elements that are the structural features of the tread that contact the ground. Such structural features may be of any type or shape, examples of which include tread blocks and tread, ribs. Tread blocks have a perimeter defined by one or more- grooves thai create an isolated, structure in the tread while a rib runs substantially in the longitudinal (circumferential) direction and is not interrupted by any grooves that run. m the substantially lateral, direction or any other grooves that are oblique thereto.
• treads and tires having such treads manufactured from a rubber composition that includes greater than 90 phr of a low Tg rubber and between 0 phr and 9 phr of an additional highly unsaturated diene elastomer.
• the additional highly unsaturated diene elastomer may be included at between 0 phr and 9 phr, between 0 phr and 5 phr or, in the ease of the rubber composition having only the low Tg rubber, 0 phr of the additional highly unsaturated diene elastomer or any other type of diene elastomer.
• SBR is a copolymer of styrene and butadiene and is one of the most commonly used, rubbers. It is typically manufactured by one of two processes ⁇ an emulsion process producing E-SB and a solution process producing S-SBR, Particular embodiments of the present invention contemplate utilizing S-SBR, E-SBR or combinations thereof as the low Tg SBR. component of the rubber composition,
• the microstructure of SBR is typically described in terms of the amount of bound styrene and the form of the butadiene portion of the polymer.
• a typical SBR that is often suitable for use in tires is around 25 wt, % bound styrene.
• Materials having a very high, content of bound styrene, e.g., around 80 wt %, are identified as high styrene resins and are not suitable as ait elastomer for manufacturing treads.
• Particular embodiments of the. present invention may utilize an SBR having a bound styrene content of between 3 wt. % and 35 wt, % or alternatively/ between 3 wt. % and 30 wt 3 ⁇ 4.
• the butadiene portion is made up of three forms: cis-1,4, 4 and vinyl- 1 * 2.
• SBR materials suitable for use as the low Tg SBR may be described as having a vinyl- 1.2-bond content of between 4 moi. % and 30 mol. % or alternatively, between 4 mol. % and 25 mol. % or between 4 moi. % and 20 mol. %.
• the processing conditions under which the polymerization takes place determines the -microstructure of the SBR. product Typically, as the styrene content and the. vinyl content of the SBR increases, the Tg of the material increases.
• the SBR that is exclusively or almost, exclusively used in the treads disclosed herein has a glass transition temperature of less than -50 °C or alternatively, less than -60 °G.
• the- SB may have a glass transition temperature of between -100 0 C and -50 °C or alternatively, between -100 °C and -55 °C, between -1 0 °C and -60 °C or between -90 °C and -50 °C,
• the glass transition temperature may also range between greater than -80 °C and -55 °C S between -75 °C and -60 °C or between -75 °C and -65 °C.
• Glass transition temperatures for the low Tg SBR are determined by differential scanning devisnetry (DSC) according to ASTM El 356,
• SBR having a low Tg examples include, for example, DURADENE 71 1 (18 % stymie, 12 % vinyl, -70 °C Tg) and DURADENE 741 (5 % styreae,. 28 % vinyl, -77 °C Tg, tin coupled polymer) that are available iron's: Firestone of Akron. OH and TUFDE E 1000 (18 % styrene, 1 1 % vinyl, -72 °C Tg) available from Asahi Chemical Company of Japan.
• Pofybutadienes that have glass transition temperatures in the same ranges as the low Tg SBR. materials described above may also he utilized similarly to the low Tg SBR,
• the glass transition temperatures of polybutadiene may be adjusted by varying the vinyl content of the polymer using methods that are well known in the art.
• Particular embodiments of the rubber compositions disclosed herein may include greater: than. 90 phr or alternatively, greater than 95 plir or 100 phr of a low Tg SBR, a low Tg polybutadiene, i.e., a polybutadiene. having the- same glass transition temperature ranges as defined above for a low Tg SBR, or combinations thereof.
• particular embodiments of the present inventio may further include an additional diene elastomer.
• the diene elastomers or rubbers that are useful for such rubber compositions are understood to be those elastomers resulting at least in part, i.e., a homopolyme . r or a copolymer, from diene monomers, i.e., monomers having two double carbon-carbon bonds, whether conjugated or not,
• diene elastomer may be classified as either "essentially unsaturated” diene elastomers or "essentially saturated” diene elastomers.
• essentially unsaturated diene elastomers are diene elastomers resulting at least in part from conjugated diene monomers, the essentially unsaturated diene elastomers having a content- of such members or units of diene origin (conjugated dienes) that is at least 15 snoi.
• essentially unsaturated diene elastomers are highly unsaturated diene elastomers, which are- diene elastomers having a content of- units of diene origin (conjugated diene) that is greater than 50 mol, %,
• diene elastomers thai do not fall into the definition of being essentially unsaturated are, therefore, the essentially saturated diene elastomers.
• elastomers include, for example, butyl, rubbers and copolymers of dienes and of alpha-olefins of the EPD type. These diene elastomers have low or very low content of units of diene origin (conjugated dienes), such content being less than 15 mob %.
• the elastomers may have any mierostmcture, which is a function, of the polymerization conditions, used., in particular of the presence or absence of a modifying and/or randomizing agent and the quantities o modifying and/or randomizing agent used.
• the elastomers may, for example, be block, random, sequential or micro-sequential elastomers, and may be prepared in dispersion or in solution; they may be coupled and/or starred or alternatively funetionalized with a coupling and/or starring or functionalizlng agent.
• these comments also apply to the low Tg SBR and polybutadienes discussed above that are useful in the present invention.
• Funetionalized rubbers i.e., those appended with active moieties, are well known in the industry.
• the backbone or the branch ends of the elastomers may be funetionalized by attaching these active moieties to the ends of the chains or to the backbone of the polymer
• Examples of fimetionalized elastomers include silanol or polysiloxane end-functionalized. elastomers, examples of which may be found in US Patent No. 6,013,718, issued January 1 1, 2000, which i hereby fully incorporated, by reference.
• funetionalized elastomers include those having alkoxysilane groups as described in US 5,977,238, carboxylic groups as described in US 6,815,473 or palyei er groups as described in US 6,503,973, all .these cited patents being incorporated herein by reference. As noted, such funciionalized elastomers are also useful as the Sow Tg SBR and poiybutadiene rubbers as well.
• Suitable diene elastomers include polybutadienes, particularly those having a content of 1,2- units of between 4 mol % and 80 mob % or those having a cis-1,4 content of more than 80 mpl, . Also included are, polyisoprenes and butadiene/isoprene copolymers, particularly those having an isoprene content of between 5 wt, % and 90 wi % and a glass transition temperature (Tg, measured in accordance with ASTM D341 S) of -40° C to -80° C,
• suitable diene elastomers for particular embodiments of the present invention include highly unsaturated diene elastomers such as polybutadienes (BR), polyisoprenes (IR), natural rubber (Nil), butadiene copolymers, isoprene copolymers and mixtures of these elastomers.
• Such copolymers include butadiene/siyrene copolymers. (SBR), isoprene/butadiene copolymers. (BIR), isoprene/styrene copolymers (SIR) and isoprene/butacHene styrene copolymers (SBIR).
• Suitable elastomers may also include any of these elastomers being functionalized elastomers.
• the additional diene elastomer included in particular -embodiments of the present invention may be one diene elastomer or a mixtiire of several diene elastomers,
• the additional, diene elastomer may further be selected from the highly unsaturated diene elastomers, the essentially unsaturated diene elastomers, the essentially saturated diene elastomers or combinations thereof.
• the rubber composition disclosed herein may further include reinforcing filler.
• Reinforcing fillers are added to rubber compositions to, inter alia, improve their tensile strength and wear resistance. Any suitable reinforcing filler may h suitable for use in compositions disclosed herein including, for example, carbon blacks and/or inorganic reinforcing fillers such as silica, with which a coupling agent, is typically associated.
• Suitable carbon blacks include, for example, those of the type HAF, ISAF and SAP, conventionally used in tires. Reinforcing blacks of ASTM grade series 10-0, 200 and/or 300 are suitable such as, for example, the blacks Nl 15, N134, N234, N330, N339, N347, M375 or alternatively, depending on the intended application, blacks of higher ASTM grade series such as N660, N683 and N772.
• inorganic reinforcing fillers include any inorganic or mineral fillers, whatever its color or origin (natural or synthetic), that are capable without any other means, other than an intermediate coupling agent, or reinforcing a rubber composition intended, for th manufacture of tires. Such inorganic reinforcing fillers can replace conventional tire-grade carbon blacks, in whole or in part, in a rubber composition intended for the manufacture of tires. Typically such fillers ma be .characterized as having, the presence of hydroxy! (-OH) -groups on its surface * [0035] Inorganic reinforcing fillers may take many useful forms including, for example, as powder, microbeads, granules, balls and/or any other suitable form as well as mixtures thereof. Examples of suitable inorganic reinforcing fillers include mineral fillers of the siliceous type* .swell as silica (SiOi), of the aluminous type* such as alumina (AIO3) or combinations thereof
• silica reinforcing fillers- known ' in the art include fumed, precipitated and/or highly dispersible silica (known as "HD" silica).
• highly dispersible silicas include Uitrasil 7000 and Ultrasii 7005 from Degussa, . the silicas Zeosi ' i 1165MP. ⁇ 35 ⁇ and 1 ⁇ 5 ⁇ from Rhodia, the silica Hi-Sil EZ15GG from PPG and the silicas Zeopoi 8715, 8745 and 8755 from Huber.
• the silica may have a BET surface area, for example, of between .60 m 2 /g and 250 m 2 /g or alternatively between 80 nrVg and 230 nr/g.
• Examples of useful reinforcing aluminas are the aluminas Baikalox A.1.25 or CR125 from Baikowski, APA-I OORDX from Condea, Aluminox ' id C from Degussa- or AKP- G015 from Sumitomo Chemicals,
• a coupling agent that is at least bi-funetional provides a sufficient chemical and/or physical connection between the inorganic reinforcement filler and the diene elastomer.
• Examples of such coupling agents include bifunctional orgaaosilanes or polyorgaaosiloxanes ' ; Such coupling agents and their use are well known in the art.
• the coupling agent may optionally be grafted beforehand onto the diene elastomer or onto the inorganic reinforcing, filler as is known. Otherwise it may be mixed into the rubber composition in its free or non-grafted state.
• One useful coupling agent is X 50-S, a. 50-50 blend by weight of Si69 (the active ingredient) and N330 carbon black, available from Evonik- Degussa.
• the coupling agent may be included at any suitable amount for the given application, examples of which are between 2 phr and 15 phr or alternatively, between 2 phr and 12 phr. It is generally desirable to minimize its use. in particular embodimenis.
• the amount of coupling agent may represent between 0.5 and 15 -wt. % relative to the total weight of the silica filler. In the case for example of tire treads for passenger vehicles, the coupling agent, may be less than 1.2 wt. % or even, less than 8 wt, % relative to the total weight of the silica filler.
• the amount of total reinforcing filler may include any suitable amount for the given application, examples of which are between 20 phr and 200 phx or. lternatively between 30 phr and 150 phr, between 90 phr and 130 phr or between 50 phr and 175 phr.
• particular embodiments of the rubber composition disclosed herein may further include a piasticizing system.
• the piasticizing system may provide both an improvement to the processabilJiy of the rubber mix and/or a means for adjusting the rubber composition's glass transition temperature and/or its rigidity.
• Suitable piasticizing systems may include a piasticizing liquid, a plasticizh g resin or. ⁇ combinations thereof.
• Suitable piasticizing liquids may include any liquid known for its piasticizing properties with, diene elastomers. At room temperature (23 e Q > these liquid plasticizers or these oils of varying viscosity are liquid as opposed to the resins that are solid. Examples include those derived from petroleum stocks, those having a vegetable base and com inations ' thereof Examples of oils that are petroleum based include aromatic oils, paraffinic oils, naphthenic oils, MES oils, TDAE oils and so forth as known in the industry. Also known are liquid diene polymers, the. polyoiefi oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and combinations of liquid plasticizers.
• suitable vegetable oils include sunflower oil, soybean oil, safflower oil, corn oil, linseed oil and cotton seed oil. These oils and other such vegetable oils may be used singularly or in combination.
• sunflower oil having a high oleic acid content (at least 70 weight, percent or alternatively, at least 80 weight percent) Is useful, an example being AGRI-PURE 80, available from Cargi . ll with offices in Minneapolis, MN.
• the selection of a suitable piasticizing oil is limited to a vegetable oil having a high oleic acid content.
• the amount of piasticizing- liquid useful in any particular embodiment of the present invention depends upon the particular circumstances and the desired result.
• the piasticizing liquid may be present in the rubber composition in an amount of between 0 or 10 phr and 60 phr or alternatively, between 0 o 10 phr and 55 pin-, between 0 or 10 phr and 50 phr, between 0 or 5 phr and 40 phr or between 0 or 10 phr and 35 phr.
• a plasiicizing hydrocarbon resin is a hydrocarbon compound that is solid at ambient temperature (e.g., 23 °C) as opposed to a liquid piastieizing compound, such as a plasiicizing oil. Additionally a plasiicizing hydrocarbon resin is. compatible, i.e., miseibie, with the rubber composition with which the resin Is mixed at a concentration that allows the resin to act as a true, plasiicizing agent, e.g., at a concentration that is typically at least 5 phr (parts per hundred parts rubber by weight).
• Plasiicizing hydrocarbon resins are polymers that can be aliphatic, aromatic or combinations of these types, meaning that the polymeric base of the resin ma be formed from aliphatic and/or aromatic monomers. These resins can be natural or synthetic materials and can be petroleum based, in which ease the resins may be called petroleum plasiicizing resins, or based on. plant materials. In particular embodiments, although not limiting the invention, these resins may contain essentially only hydrogen and carbon. atoms.
• the plasiicizing hydrocarbon resins- useful in particular embodiment of the present invention include those thai are .homopolymers or copolymers of eyclopentadiene (CPD) or dicyclopentadiene (DCPD), homopolymers or copolymers of terpens, homopolymers or copolymers of C$ cut and mixtures thereof
• CPD eyclopentadiene
• DCPD dicyclopentadiene
• Such copolymer plasiicizing hydrocarbon resins as discussed generally above may include, for example, resins .made up of copolymers of (D)CPD/ vinyl-aromatic, of (D)CPD terpene, of (D)CPD/ Cj cut, of terpene/ vinyl-aromatic, of Cj cut/ vinyl -aromatic and of combinations thereof.
• Terpene monomers useful for the terpene homopofymer and copolymer resins include alpha-p nene, beta-pinene and liraonene.
• Particular embodiments include polymers of the limoneiie monomers that include three isomers: the. L-iimonene (laevorotaiory enantiomer), the D-liraonene (dextrorotatory enantiorner), or even the dipentene, racemie mixture of the dextrorotator and laevorotatory enaniiomers.
• vinyl aromatic monomers include styrene, alpha- metbylstyrene, oriho-, meta-, para-meihylsiyrene, vinyl-toluene, para-tertiohutyistyrene, methoxystyrenes, chloro-styrenes, vinyl-mesitylene, diVinyibenzene, vinylnaphfhalene, any vinyl-aromatic monomer coming from the Cg cut (or, more generally, from a C3 ⁇ 4 to Cjo cut).
• Particular embodiments that include a vinyl-aromatic copolymer include the vinyl -aromatic in the minority monomer, expressed in molar fraction, in the copolymer.
• Particular embodiments of th present invention include as the plastlcizkg hydrocarbon resin the (D)CPD homopolytner resins, the (D)CPD/ styrene copolymer resins,, the poiylimonene resins, the limonene/ styrene. copolymer resins, the limonene/ D(CPP) copolymer resins, C3 ⁇ 4 cut/ styrene copolymer resins, Cj cut/ ( 3 ⁇ 4 cut copolymer resins, and mixtures thereof,
• piasUcizing resins tha include terpene resins suitable for use in the present invention Include a poiyalphapinene resin marketed under the name Resin R2495 by Hercules Inc. of Wilmington, DE. Resin R2495 has a molecular weight of about 932, a softening point of about !3S°C and a glass transition temperature of about 91°C.
• Resin R2495 has a molecular weight of about 932, a softening point of about !3S°C and a glass transition temperature of about 91°C.
• Another commercially available product that may be used in the present invention includes DERCOLYTE L120 sold by the company DRT of France.
• DERCOLYTE L120 polyterpene- lim.oriene resin has a number average molecular weight of about 625, a weight average molecular weight of about 1010, an Ip of about 1.6, a softening point, of about 1 1 °C and has a glass transition temperature of about 72° C.
• Still another commercially available terpene resin that may be used in the present invention includes SYLVARES TR 7125 and/or SYLVARES TR 5147 poiylimonene resin sold by the Arizona Chemical Company of Jacksonville, FL.
• SYLVARES 7125 poiylimonene res n has a molecular weight of about 1090, has a softening point of about 125° C. and has . a glass transition temperature of about 73°C while the SYLVARES TR 5147 has a molecular weight of about 945, a softening point of about 120 °C and has a glass transition temperature of about 71 ° C.
• Cs cut/ vinyl-aromatic styrene copolymer notably (3 ⁇ 4 cut / styrene or C3 ⁇ 4 cut / 3 ⁇ 4 cut .from.
• Neville Chemical Company under the names SUPER NEVTAC 78, SUPER NEVTAC 85 and SUPER NEVTAC 99; from Goodyear Chemicals under the name WINGTACK EXTRA; from oion under names HIKOREZ T1G95 and HIKOREZ Ti l 00;. and from Exxon under names ESCOREZ 2101 and ECR 373..
• Suitable plastieizing hydrocarbon resins that are limonene slyrene copolymer resins that are commercially available include DBRCOLYTE TS 105 from DRT of France; and from Arizona Chemical Company under the name ZT115LT and ZT5100.
• temperatures of plastieizing resins may be measured by Differential Scanning Galorimeiry (DCS) in accordance with ASTM D3418 (1999).
• useful resins may be have a glass transition temperature that is at least 25° C or alternatively, at least 40° C or at least 60° C or between 25° C and 95° C, between 40° C and 85° C or between 60° C and 80° C.
• The. amount of plastieizing hydrocarbon resin useful in any particular embodiment of the present invention depends upon the particular circumstances and the desired result.
• the plastieizing hydrocarbon resin may be present in the rubber composition in an amount of between 5 phr and 120 phr or alternatively, between 5 phr and 1.00 phr or between 5 phr and 60 phr.
• the plastieizing hydrocarbon resin may be present in an amount of between 5 phr and 70 in; between 25 phr and 55 phr, between 20 phr and 70 ph .
• the rubber compositions disclosed herein may be cured with any suitable curing system including a peroxide curing system or a sulfur curling system. Particular .embodiments are cured with a .sulfur curing system that includes free sulfur and may further include, for example, one or more of accelerators, stearic acid and zinc oxide.
• Suitable tree sulfur includes, ⁇ for example, pulverized sulfur, rubbe maker's sulfur, commercial sulfur, and insoluble sulfur.
• the amount of tree sulfur included in the rubber composition is not limited, and may range, for example, between 0.5 phr and 10 phr or alternatively between 0.5 phr and 5 phr or between 0.5 phr and 3 phr, Particular embodiments may include no free sulfur added in the curing system but instead include sulfur donors.
• Accelerators are used to control the time and/or temperature required for vulcanization and to improve the properties of the cured rubber composition.
• Particular embodiments of the present invention include one or more accelerators.
• One example of a suitable primary accelerator useful in the present invention is sulfenamide.
• Suitable sulfenamide accelerators include n-cyclohexyl » 2-bet3 ⁇ 4zo.ihiazole sulfenamide (CBS), - terl-buiy]-2-benzoihia3 ⁇ 4Qlc .Su!tenamide (TBBS), N-OxydiethyW-benzthiazolsulfenamid (MBS) and N' ⁇ dicyciohexyl"2-benzothiazoiesulft!naniide (DCBS).
• Combinations of accelerators are often useful, to improve the properties of the cured rubber composition and the particular embodiments include the addition of secondary accelerators.
• Particular embodiments may include as a secondary accelerant the use of a moderately fast accelerator such as, for example, diphenylguanidiue (DPG), tripheny) guanidine (TPG), diorthoioiyi guanidine (DOTG), o-tolylbigautude (OTBG) or hexamethylene tetramine (HMTA).
• a moderately fast accelerator such as, for example, diphenylguanidiue (DPG), tripheny) guanidine (TPG), diorthoioiyi guanidine (DOTG), o-tolylbigautude (OTBG) or hexamethylene tetramine (HMTA).
• DPG diphenylguanidiue
• TPG tripheny) guanidine
• DDG diorthoioiyi guanidine
• OTBG o-tolylbigautude
• HMTA hexamethylene tetramine
• additives can be added to the rubber compositions disclosed herein as known in the art.
• Such additives may include, for example, some or all of the following * antidegradants.
• antioxidants include 6 ⁇ . ⁇ . ⁇ 77PD, IPPD and TMQ and may be added t rubber compositions in an amount, for example, of from 0.5 phr and 5 phr.
• Zinc oxide may be added in. an amount, for example, of between 1 phr and 6 phr r alternatively, of between 1 .5 ph and 4 phr.
• Waxes may be added i n an amount, for example, of between 1 phr and 5 phr,
• the rubber compositions that are embodiments of the present invention may be. produced in suitable mixers, in a manner known to those having ordinary skill in the art, typically using two successive preparation phases, a first phase of thermo-mechanicai working at high temperature, followed by a second phase of mechanical working at lower temperature,
• thermo-mechanicai working (sometimes referred to as "nonproductive" phase) is intended to mix thoroughly, by kneading, the various ingredients of the composition, with the exception of the vulcanization system, it is carried out in a suitable kneading device, such as an internal mixer or an extruder, until, under the action of the mechanical working and the high shearing imposed on the mixture, a maximum temperature generally between 120° C and 190° C, more narrowly between 130° C and 170° C, is reached.
• a second phase of mechanical working- is implemented at a lower temperature.
• this finishing phase consists of incorporating by mixing the vulcanization (or cross-linking) system (sulfur or other vulcanizing agent and accelerators) ⁇ , in a suitable- device, for example- a open mill.. It is performed for an appropriate time (typically- between 1 and 30 minutes, for example between 2 and 10 minutes) and at a sufficiently low temperature lower than the vulcanization temperatur of the mixture, so as to protect against premature vulcanization.
• a suitable- device for example- a open mill.
• the rubber composition can be formed into useful articles, including treads for use on vehicle tires.
• the treads may be formed as tread bands and then later made a part of a tire or they be formed directly onto a tire carcass by, for example, extrusion and the cured in a mold.
• tread bands may be cured before being disposed on a fire carcass or they may be cured after being disposed on the tire carcass.
• a tire- tread . is cured in a known manner in a mold that molds the tread elements into the tread, including, -e.g., the. sip.es molded into the tread blocks.
• treads may be formed from only one rubber composition or in two or more layers of differing rubber compositions, e.g., a cap and base construction, in a ca and. base construction, the cap portion of the tread is- made of one rubber composition that is designed, for contact with, the road.
• the cap is supported on the base portion of the tread, the base portion made of a different rubber composition, in particular embodiments of the present invention the entire- tread may be made from the rubber compositions as disclosed herein while in other embodiments only the cap portions of the tread may be made from such rubber compositions.
• a tread block may be formed totally from the rubber composition having the low Tg as disclosed herein, may be formed totally from another rubber composition o may be formed as combinations thereof.
• a tread block may be: formed as a composite of layered rubber -compositions, such that half of the block laterally is a layer of the low Tg rubber composition and the other half of the block laterally is a layer of an alternative rubber composition. Such construction would provide a tread block having 80 percent of its contact surface formed of the lo w Tg rubber composition.
• At least 80 percent of the total contact surface- of all the tread blocks on a. tread may he .formed from the rubber composition having the low Tg as disclosed herein.
• at least 90 percent, at least 95 percent or 100 percent of the total contact surface of all the tread blocks on a tread may be formed from such rubber composition.
• tire treads disclosed herein are suitable for many types of vehicles, particular embodiments include tire treads for use on vehicles such as passenger cars and/or light trucks. Such tire treads are also .useful for all weather tires, snow tires -and/or warm weather tires. As such, the .properties of the -cured rubber compositions from which the treads disclosed herein may be .manufactured may have a glass transition temperature of between -35° C and - 25° C and/or alternatively, between -28° C and -14° C, between -30° C and -16° C and/or betwee -16° C and 10° C.
• such, rubber composition may further he characterized as having a shear modulus G* measured, at 60° C of between 0.5 MPa and 2 MPa or alternatively, 0.5 MPa and 1.5 MPa, between 0.5 MPa and 1.2 MPa or 0.6 MPa and 1.1 MPa,
• Modulus of elongation was measured at 10% (MA 10) at a temperature of 23 °C based on ASTM Standard D412 on dumb bell test pieces. The measurements were taken in the second .elongation; i.e., after an accommodation cycle, These measurements are secant, moduli in MPa, based on the original cross section of the test piece.
• Wear resistance of a tire mounted- on. an automobile was measured by subjecting the fire to actual on-rosd travel and measurin its wear rate -(mm of tread lost per 1000 miles) at between 10,000 and 12,000 miles traveled. A value greater than that: of the control, arbitrarily set to 100, indicates an improved result,, that is to say less wear rate.
• Rubber compositions were .prepared using the components shown in Table 1, The amount of each component making u the rubber compositions .shown in Table 1 are provided in parts per hundred parts of rubber by weight (phr). The microstaictures and glass transition temperatures of each S-SBR is also provided in Table 1.
• the terpens resin was SYLVARES "TR-5147, a polylimonene resin, available from Arizona Chemical, Savannah, GA,
• the plasticizing oil was naphthenic- oil and/or sunflower oil.
• the silica was ZBOSJL 160 3 a highly dispersible silica .available from Rhodia having a BET of 160 m 2 /g.
• the piasticizing oil was AGRI-PURE 80.
• the silane coupling agent was X 50-S available, from Evonik Degussa.
• the curative package included sulfur, accelerators, zinc oxide and stearic acid. Table 1 - Rubber Formulations
• the rubber fonnulatioas were prepared by mixing the components given In. Table .1 , except for the sulfur and the accelerators, in a Banbury mixer operating between 25 and 65 RPM until a temperature of between 130° C and 1 70° C was reached.
• the accelerators and suifur were added in the second phase o a -mil!. Vulcanization was effected at 1 0° C for 40 minutes.
• the formulations were then tested to measure their physical properties, the results of which are shown i Table 1.
• FIG. 1 is a graph that compares the wet braking and wear performance for tires having treads manufactured from different rubber compositions.
• Tires (Primacy MXV4 201/55R 1 ) were manufactured usin each, of the formulations F1-F4 shown in Table 1. The tires were tested fo their wet braking and wear performance in accordance with the test procedures described above. As the glass transition temperature of tire SBE. was lowered-, the results clearly demonstrate the surprising break in the wear/wet braking compromise.

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• 2011
  • 2011-09-14 US US14/345,213 patent/US20150283854A1/en not_active Abandoned
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